I need to know How I can create a Custom grid only with some fields of a table, not all fields.

You can use DBPro's dbpSetColumnOrder action to limit the grid display to specific fields. The dbpSetGridProperties, dbpSetColumnWidths and other actions can be used to further customize the grid's appearance.

I need too to know how can I open a database to allow all users to open it automatically. The database is on the same app directory allways but I would like to avoid to specify the full databae path.

Use NeoBook's [PubDir] global variable instead of a literal path. For example: